Master cylinders and power boosters such as those commonly used in brake and clutch systems are usually actuated by means of a push rod connected to be actuated in the apply direction by a pedal. The push rod, having one end connected to a pedal arm which swings in an arc about a pedal pivot, has that end moving pivotally in a plane as well as axially as the pedal is pressed. The other end usually has a ball end on it and is attached to a master cylinder piston or a power booster control valve which moves axially in a cylinder. Thus that rod other end is restricted to linear movement along the axis of that cylinder. For this reason, that rod other end is commonly made with a ball end which fits in a socket in the master cylinder piston or the power booster control valve, the arrangement being such that the necessary pivotal movement of the rod is accommodated.
The ball end of the rod is retained in the piston or valve in any of several manners. One example is that of staking the ball in place by a staking operation in which one or more parts of the power booster valve are displaced radially inward so that a permanent barrier to removal of the rod is provided. The rod ball end engages that staked barrier when the rod is subjected to tension force tending to retract the rod from the valve, thus moving the valve with any attempted retracting movement of the rod. This has an advantage of simplicity and no additional parts, but has disadvantages in that the rod cannot be removed while leaving the valve intact; the staking process cannot be sufficiently accurate to obtain the depth of staking needed along with the location of the staked valve material so that there is a minimum looseness in fit between the rod ball end and the valve but not a binding fit between them. This staking arrangement has been used in power brake boosters, particularly of the vacuum suspended type in which the push rod is secured to the air valve of the booster, for many years. U.S. Pat. No. 3,068,842, entitled, "Brake Booster Unit" and issued Dec. 18, 1962 to Frank W. Brooks shows the staking arrangement in an air suspended power booster.
This arrangement and other typical arrangements for securing the ball end in place are shown in various ones of the following U.S. Pat. Nos.:
U.S. Pat. No. 3,050,035, entitled, "Brake Booster Valve" and issued Aug. 21, 1962 to Carl E. Wilkins et al;
U.S. Pat. No. 3,052,130, entitled, "Pedal Connection" and issued Sept. 4, 1962 to George E. Kellogg et al;
U.S. Pat. No. 3,350,882, entitled, "Vehicle Braking System" and issued Nov. 7, 1967 to Maurice B. Leising;
U.S. Pat. No. 3,410,178, entitled, "Valve Means for a Fluid Pressure Servomotor" and issued Nov. 12, 1968 to Oswald O. Kytta;
U.S. Pat. No. 3,733,822, entitled, "Dual Ratio Force Transfer Apparatus" and issued May 22, 1973 to William E. Monroe;
and U.S. Pat. No. 3,807,280, entitled, "Servo Motors" and issued Apr. 30, 1974 to Ronald F. Green et al.
It is to be understood that these patents are merely typical of the arrangements being used or otherwise forming a part of the prior art, and that there are a multitude of patents disclosing master cylinders, power boosters and other mechanisms with such arrangements.
U.S. Pat. No. 3,050,035 shows a metal clip which fits in ball-and-socket relation about the enlarged ball end of the push rod and then is press fitted into the bore of the air valve member of the booster.
U.S. Pat. No. 3,052,130 discloses a push rod extending forwardly into an opening extending on the rearward end of the master cylinder piston. The push rod has a groove behind its spherical end which is engaged by a retainer ring through which the end of the push rod was extended. The retainer ring appears to be a hollow rubber cone with the top of the cone removed so that the push rod extends through it, the retainer ring having been earlier installed in the piston opening.
U.S. Pat. No. 3,350,882 discloses a plunger having a bore which receives a relatively resilient retainer (which in common production practice is a synthetic rubber retainer) installed in the bottom end of the bore. The generally spherical ball end of the brake pedal rod is received in the resilient retainer. A cup-like retainer (illustrated as a metal retainer) is illustrated as being fitted over the brake pedal rod so that it is smaller than the ball end of the rod and engages the resilient retainer. The cup-like retainer is tightly fitted (apparently a press fit) into the bore of the plunger and serves to retain the resilient retainer in the position illustrated.
U.S. Pat. No. 3,410,178 shows the staking arrangement discussed above. This patent and U.S. Pat. No. 3,733,822 also show the same type of retainer as that in U.S. Pat. No. 3,350,882 discussed above.
U.S. Pat. No. 3,807,280 illustrates and describes a valve member having a threaded recess with a thrust member threaded into it and abutting a shoulder in the recess. The ball end of the push rod fits in a hemispherical socket in the thrust member and a split ring collar surrounds the push rod just behind the ball end. The collar has a part-spherical inner configuration which frictionally engages the push rod ball end. An inner member is also threaded into the recess, engaging the split ring so as to hold it in frictional engagement with the push rod ball end.